This Program Project Grant is designed to provide information on the metabolism and mode of action of five different types of pest control agents important in establishing conditions for their safe and efficient use. Studies on synthetic pyrethroids will emphasize the metabolic fate and photodecomposition of permethrin, the first photostable pyrethroid for potential use in agriculture. It also concerns pyrethroid structure-biodegradability relationships. More than 1 billion pounds of toxaphene have been used over the past 25 years, so this complex mixture continues to be the focal point in studies on chlorinated hydrocarbons, particularly as to its metabolic fate in mammals, synthesis of toxic components and photodecomposition. The studies on respiratory inhibitors are focused on organotin pesticide chemicals and related compounds, with special emphasis on the complex metabolic pathways involved in the detoxification of tributyltin and tricyclohexyltin derivatives, both important biocides. Research on organophosphorus insecticides is continuing on dioxathion metabolism and photochemistry, mechanisms involved in teratogenesis and delayed neurotoxicity, and mode of action studies on highly toxic bicyclic compounds. Other toxicants under investigation as to their mode of action are the benzoylurea inhibitors of chitin synthesis, thiocarbamate herbicides, and the antidotes for thiocarbamate herbicides. These studies involve synthesis of labeled pesticides and of unlabeled metabolites and photoalteration products and many types of toxicity testing and biochemical considerations. BIBLIOGRAPHIC REFERENCES: Ohsawa, T., J. R. Knox, S. Khalifa and J. E. Casida. 1975. Metabolic dechlorination of toxaphene in rats. J. Agr. Food Chem. 23:98-106. Casida, J. E., E. C. Kimmel, H. Ohkawa and R. Ohkawa. 1975. Sulfoxidation of thiocarbamate herbicides and metabolism of thiocarbamate sulfoxides in living mice and liver enzyme systems. Pesticide Biochem. Physiol. 5:1-11.